Superheated Water


Put simply, superheating involves raising the temperature of a liquid, for instance, beyond its boiling point without allowing it to vaporize. This can be done by heating water in a sealed container above 100 Celsius. There is an urban myth that has done the rounds for many years that it is possible to superheat the contents of a liquid-filled cup in a microwave and trigger a geyser of fluid when you remove it and stir. Who hasn’t received the spam-mail describing the 26-year old who was severely disfigured by such an incident?

Well, there are risks associated with all cooking, and heating a liquid in a microwave for long enough will produce a boiling temperature liquid and a container surface coated with scalding hot “condensation” that could cause you to jolt and end up splashing yourself with scalding liquid.

Apparently, it happens, so be careful. However, I think it would be hard to actually “superheat” the liquid, although the guys in this video may have done just that using pure, distilled water or similar.

The liquid would have have no so-called “nucleation” points, specks of dust, particles, or whatever, even scratches inside the beaker to seed bubbles of steam. The water could very easily surpass its boiling point without actually boiling.

Like Snopes says, it is possible but takes a lot of effort to cause superheating in a normal cup under normal conditions in a microwave oven. Nevertheless, it’s not worth risking a scalding in an attempt to duplicate the above experiment with your morning coffee.

10 thoughts on “Superheated Water”

  1. Well,
    I was heating up water for a cup of tea and the microwave oven door burst open with a bang, water water everywhere! I googled it and confirmed the theory that the water in my cup had become super heated. Particulars: I’d heated the water for about 2 minutes earlier, then forgot about it, when I remembered, about 20 minutes later, it had cooled to the point that I figured my tea wouldn’t steep well, so I set the timer for 3 minutes, all the while talking with one of my co-workers, I thought that the water was taking quite awhile to heat up, no boiling, no bubbling, nothing, then suddenly, boom! the door flew open and water was everywhere. It was in a ceramic cup, about 3/4 full bottled drinking water. I didn’t touch it, didn’t add anything to it, just plain ole undisturbed water heating up in a regular old clean coffee cup in a regular old microwave oven. SH*T happened… big wet mess. Fortunately no’one was in the path of the super heated water as it flew from the microwave.

  2. Hello. I have one question for you. What will happen if I pour in some super heated water in super cooled water.. what could happen. I am a student at Physics in Romania and I am going to try making this experiment and study some proprieties during the process of instant freezing. Waiting for some opinions.

  3. Roger, sounds like your wife was very lucky…but…why on earth was she heating a glass of water in the microwave oven, and for that long, four and a half minutes? Jeeez, it was bound to do something dramatic, I’d use a kettle in future, it’s what they’re designed for…

  4. My wife put about 1 and 3/4 cups of water heating in a pyrex glass measuring cup,into the microwave. She heated it about four and a half minutes.When she opened the door and took the water out it exploded. I was in the other room and heard the explosion. Sounded like a twelve gauge going off. The water all came out the cup severly burning her right arm. Thank god it didn’t hit her face. She has first to second degree burns on her arm. This was water straight from the faucet.Her clothing kept her leg from getting really burned. I have used microwaves for over 30 years and have never witnessed this before.

  5. I had this happen to me, and it really doesn’t take much.
    I set the timer for four minutes, since it was a large Pyrex container of water.
    I opened the microwave door and the cooler outside air disturbed the already unstable surface tension of the heated water. I was very lucky I didn’t get badly burned.

  6. I do specifically state in the article that’s it’s not worth risking a scalding attempting this experiment. I and the Snopes article and others do say that it’s potentially dangerous.

  7. I am as of now sporting a 6″ x 8″ scald on my side as a result of heating ” plain ole well water” in a microwave. Folks it exploded “not fizzled or boiled “out of the cup. Knocked the door completely wide open and caused the wife to nearly take out the refrig. from the sound of the thud frightning her. Believe me you don”t want to let your kids do this . This surely would disfigure or blind them ,as it would probally hit them in the face.
    This was after heating for only 2 and 1/2 min. on high. The water has been filtered when it came into the house and was in a heavy cup , but nothing to account for all that.
    I am 53 years old and have worked on large steam boilers and other such things, all my adult life, and this was one of the more violent and unexpected accidents I have run across .

  8. In my personal experience a clean glass filled with ordinary (faucet) water boils differently in microwave than in a pot over a gas flame. Heated in a microwave owen the bubles in the water are much bigger and there’s a lot less of them compared to water boiling over a flame. I guess it’s because glass & water in it is much cleaner giving the water less opprtunities to create bubbles. As to why adding salt (or almost anything) to this “superheated” water may be dangerous: a) you create lots nucleaton centers and b) dissolving salts usually produces energy, rather than consuming it thus heaing the water ever more and sometimes, when the water is very close to its boiling point creating a dangerous small scale explosion, water discharging its excess energy in the now abundant nucleation centers.

    Martin from Slovakia.

  9. Fellow blogger The Homely Scientist has issued a warning that my post is just plain wrong as he experienced a scalding after heating a drink too long in the microwave. So, yes, admittedly, it is possible to overheat (not necessarily superheat) a liquid and yes, it’s a good idea to be very careful with liquids and microwaves.

    I’ve edited the post accordingly.

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